MEMS devices, such as capacitive microphones, are widely used in mobile phones or other electronic products to receive and convert sound waves into electrical signals. Generally, such a microphone includes one or two back plates (electrodes), and a moveable diaphragm separated from the back plate(s) for forming a capacitor.
When the diaphragm is actuated to vibrate relative to the back plate(s) by sound pressure, a distance from the diaphragm to the back plate is changed, and as a result, the capacitance value of the capacitor is accordingly changed, by which voice waves are converted into electrical signals. The diaphragm of the microphone with specific characteristics such as dimension, thickness and rigidity, however, is designed to sense voice waves within a narrow pressure range such as low sound pressure or high sound pressure. Thus, when a wide range of sound pressure encompassing low sound pressure and high sound pressure is required to be sensed, multiple microphones with different specifications are required to independently sense low sound pressure and high sound pressure, which increases layout area of MEMS device.